- Researchers develop a wood-based material by combining graphite with nanocellulose.
- It is stronger and 6 times lighter than stainless steel.
- It could be a green alternative for constructing lightweight body armor, vehicles and aircraft.
Materials make up the modern world around us, from advanced carbon fiber and ceramics in high-performance vehicles to concrete in buildings and bridges, and even to the nanoparticles in self-cleaning bricks.
In recent decades, materials research has changed how we design, build and use new products. But more breakthroughs in material science and engineering are needed to shape the future.
Now researchers at the University of Maryland, Rice University, University of California Merced, have shown that next-generation materials need not be as exotic as topological metamaterials and insulators.
They have built a “wonder” material by combining graphite with nanocellulose – a light solid substance extracted from plant matter which contains nanosized cellulose fibrils. Surprisingly, its material properties are superior to established structural materials such as steels, titanium alloys, and carbon fibers.
Why Wood Nanocellulose?
The strength of structural materials comes from their primary chemical bonds between their atoms: ionic bonds in ceramics, covalent bonds in carbon fibers, and metallic bonds in metal alloys.
These strong bonds have both advantages and disadvantages. They are mostly used for building high strength components that last for several decades. To recycle these materials, however, their bonds must of distorted and reformed. This process consumes massive amounts of energy, leading to a significant environmental footprint and a large cost.
The new material, on the other hand, utilizes secondary chemical bonds like hydrogen bonds. They are abundant in organic substances, such as nanocellulose. The nanocellulose used in this study is composed of cellulose fibers that are several micrometers long and 5-20 nanometers wide.
Wood-based materials have extraordinary properties: they are biocompatible, biodegradable and recyclable. Now, researches have proved that these materials can also exhibit superior performance to that of conventional materials.
While the network of hydrogen bonds make materials incredibly strong, an individual hydrogen bond can be formed or distorted using much less energy than that of a primary chemical bond.
Constructing A Strong Wood-Based Material
Researchers harnessed hydrogen bonds to ‘glue’ nanocellulose to graphite. They prepared a semi-liquid mixture of nanocellulose and graphite flakes at room temperature to fabricate a graphite-nanocellulose composite.
The mixture was then cast-printed into a flexible layer. Each layer is 20 micrometers thick and about a meter in length. And it’s possible to hot-press several layers into thicker sheets.
The resulting material is stronger and 6 times lighter than stainless steel. In fact, its specific strength is higher than materials used in structural applications, such as titanium and aluminum alloys. It could be a green alternative for constructing lightweight body armor, vehicles and aircraft.
Courtesy of researchers
To reveal its microscopic structure, researchers used a combination of transmission electron microscopy, atomic force microscopy, and molecular dynamics simulations. They found that the structure resembles a wall of bricks, where graphite flakes (gray) are the bricks, and nanocellulose fibers (green) are the mortar that holds these 100-micrometer-sized bricks together.
Fabrication of this wood-based material does not require any harsh chemicals, but it’s quite an expensive process. The team is currently working on cheaper methods to produce it on a bigger scale.